​Bio-efficacy of Chemical Insecticides and Biopesticides against Gram Pod Borer, Helicoverpa armigera (Hubner) and Spotted Pod Borer, Maruca testulalis (Geyer) on Greengram, [Vigna radiata (L.) Wilczek]

Greengram [Vigna radiata (L.) Wilczek] (family: Leguminosae) is one of the most important Kharif pulse crop grown in India. It is cultivated across seasons in different environments and in variable soil conditions in the South and South-East Asia, Africa, South America and Australia (Parihar et al., 2017). It is one of the most widely cultivated pulse crop after chickpea and pigeonpea (Swaminathan et al., 2012). In India, during 2018-19 the total area and production of pulses is 29.03 million hectares, 23.39 million tonnes but greengram occupied 47.56 thousand hectares, 2339.75 thousand tonnes (Anonymous, 2019). The major producing states in India being Andhra Pradesh, Orissa, Maharashtra, Madhya Pradesh and Rajasthan accounting for about 70 per cent of total production.
       
About 65 species of insects has been recorded on greengram (Siddapaji et al., 1979). The insect pests exercising heavy toll of greengram crop include pod borer complex viz, gram pod borer, Helicoverpa armigera (Hubner), blue butter fly, Lampides boeticus L., spotted pod borer, Maruca testulalis (Geyer), pod bug, Riptortus spp. are major pests of greengram (Sundararajan and Chitra 2017). Gram pod borer, H. armigera is widely distributed throughout India and has been recorded feeding on 181 cultivated and uncultivated plant species belonging to 45 families (Manjunath et al., 1989). Sixty cultivated and sixty-seven wild host plants attacked by H. armigera have been recorded from India (Karim, 2000). Spotted pod borer, M. testulalis attributed to the regular outbreaks of greengram because of its extensive host range and destructiveness; it became a persistent pest in greengram. It is reported that 20-30 per cent pod damage in greengram is caused due to spotted pod borer (Zahid et al., 2008).
       
It is a common observation that the population of pod borers is brought down by the application of chemical insecticides and botanicals. The present study is an attempt at chemical insecticides and biopesticides were evaluated against pod borer complex with seed yield of greengram as well as at decipher the economics of different treatments.

The present investigation was conducted at Agronomy Farm, S.K.N. College of Agriculture, Jobner, Rajasthan, India during kharif, 2018. The fertilizers and other cultural practices were followed as per the recommendations in the package of practices of Rajasthan. The experiment was laid out in a simple randomized block design (RBD) with nine treatments and each treatment replicated thrice. The individual plot size was 3.0 m × 2.5 m, keeping row to row and plant to plant distance of 30 cm and 10 cm, respectively. The seeds of greengram variety, IPM-02-03 were sown on first week of July.
 
Method of observation
 
The observations on larval populations of gram pod borer, H. armigera and spotted pod borer, M. testulalis were recorded from their appearance to harvesting of the greengram crop. For this purpose, ten plants were randomly selected from each plot and tagged. The incidence of H. armigera and M. testulalis was determined by counting the population of larvae on ten randomly selected tagged plants at weekly interval. The observations on pod borers population were recorded regularly one day before and 1, 3, 7 and 15 days after application of insecticides and biopesticides in both the sprays. The incidence was also studied in terms of mean pod damage by counting the total number of pods and damage pods on ten randomly selected tagged plants and mean damage was calculated by using the following formula:
 
The infestation was expressed as a percentage:
   
Interpretation of data
 
The population data thus recorded was converted to per cent reduction in population using the method utilized by Henderson and Tilton (1955). The statistical analysis (analysis of variance) was carried out by transforming the data of per cent reduction into angular transformation values (Gomez and Gomez, 1976). The data of seed yield influenced as a result of application of different treatments were also subjected to analysis of variance.
       
The avoidable loss and increase in seed yield over control was calculated for each treatment by the following formula:
                               
These formulae do not give the exact losses/ increase in yield because even in the best treatment some damage occurs. However, this is considered to be the most feasible method (Pradhan, 1964). The economics of each treatment was worked out by computing the cost of insecticides as well as their cost of application. The gross income was worked out by multiplying the yield with the whole sale rate of greengram seed prevailing at the time of threshing.

The bioefficacy of different treatments were evaluated on the basis of per cent reduction of pod borers population on greengram.
 
First spray of insecticides and biopesticides
 
The pre treatment population of pod borer recorded ranged between 8 to 11 larvae for gram Pod borer, H. armigera and 13 to 17 larvae for spotted pod borer, M. testulalis. One day after application of treatments (Table 1), it was observed that all the treatments were found significantly superior over the untreated control. However, their existed a considerable difference in between the different insecticidal treatments. Maximum per cent reduction of H. armigera and M. testulalis population after three days of insecticidal application was recorded in all treatment and it ranged from 33.54 to 73.42 per cent reduction in pod borer population and proved significantly superior over control. The maximum reduction 73.42 per cent recorded in spinosad 0.01 per cent treated plots. Agale et al., (2021) reported that spinosad 45 SC was most effective against H. armigera in pigeonpea. The next effective treatment was indoxacarb 0.01 per cent (71.39 per cent reduction) followed by fipronil 0.01 per cent (70.12 per cent reduction) which were at par with each other. The present findings are in agreement with that of Umbarkar and Parsana (2014) who reported that the spinosad 45 SC and indoxacarb 14.5 SC was the most effective and NSKE 10 per cent moderately effective insecticide in suppression of M. testulalis population on greengram. The Ha NPV 1 ml/ l reduction with 66.67 per cent reduction, azadirachtin 5 ml/ l with 61.53 per cent reduction, NSKE 10.00 per cent with 60.13 per cent reduction, neem oil 1.00 per cent with 55.94 per cent reduction and were at par with each other. Yadav et al., (2015) reported that novaluron, difllubenzuron, NSKE and Metarrhizium anisopliae were least effective against sucking insect pests in clusterbean. Turkhade et al., (2014) reported that the treatment azadirachtin 300 ppm @ 5ml/ l is moderately effective against H. armigera.
 

       
After seven days of application, all the treatments proved significantly superior in reducing the population of gram pod borer and spotted pod borer in the field. The maximum reduction 70.25 per cent was recorded in the treatment of spinosad 0.01 per cent. The next effective treatment was indoxacarb 0.01 per cent with 67.33 per cent reduction and fipronil 0.01 per cent with 67.10 per cent reduction followed by Ha NPV 1 ml/ l with 63.31 per cent reduction, azadirachtin 5 ml/ l with 58.97 per cent reduction, NSKE 10.00 per cent with 57.48 per cent reduction and neem oil 1.00 per cent with 53.97 per cent reduction, which were at par with each other. Kaushik et al., (2016). Mittal and Ujagir (2005) reported that spinosad is most effective treatment in reducing M. testulalis population. Srihari and Patnaik (2006) found that the indoxacarb, spinosad gave the greatest reduction in larval population of M. testulalis. The neem leaf extract 10.00 per cent was recorded with 35.82 per cent reduction, B. bassiana 1 g/ l with 30.14 per cent reduction and were at par with each other.
       
After fifteen days, maximum reduction in gram pod borer and spotted pod borer was found in  spinosad 0.01 per cent treated plots (65.65 per cent reduction) followed by indoxacard 0.01 per cent (63.04 per cent reduction) and fipronil 0.01 per cent (61.87 per cent). Dabariya et al., (2010) reported that indoxacard 0.0075 per cent gave highest per cent mortality of H. armigera followed by spinosad 0.009 per cent, profenophos + cypermethrin 0.044 per cent and endosulfan 0.07 per cent in pigeonpea. The next effective treatments were Ha NPV 1 ml/ l with 58.77 per cent reduction, azadirachtin 5 ml/ l with 58.81 per cent reduction, NSKE 10.00 per cent with 54.20 per cent reduction, neem oil 1.00 per cent was 51.71 per cent reduction and all were at par with each other. The findings are in close agreement with Padmanaban and Arora (2002) who reported 3 sprays at weekly interval of Ha NPV 375 LE ha^-1 significantly lower larval population of 0.83/ ten plants. Jayaraj et al., (1987) reported 5 sprays of 250 LE Ha NPV at weekly intervals gave satisfactory results against H. armigera. Similar results was noticed by Gopali (1998). Deshmukh et al., (2010) found that flubendiamide 0.007 per cent was most effective in reducing the H. armigera population and pod damage in pigeonpea.
 
Second spray of insecticides and biopesticides
 
The maximum reduction of 74.46 per cent was recorded after one day in spinosad 0.01 per cent followed by indoxocarb 0.01 per cent and fipronil 0.01 per cent i.e. 72.52 per cent, 71.29 per cent reduction, respectively. The next effective treatments were Ha NPV 1 ml/ l, azadirachtin 5 ml/ l, NSKE 10.00 per cent, neem oil 1.00 per cent with 67.98, 63.04, 61.69 and 57.67 per cent reduction respectively, which were at par with each other. The minimum reduction was recorded in plots treated with neem leaf extract 10.00 per cent was 35.82 per cent reduction and B. bassiana 1 g/ l was 30.14 per cent reduction which was inferior to all the other insecticidal treatments. All the treatments significantly reduced the gram pod borer and spotted pod borer damage after three days of treatment and the per cent reduction ranged from 37.93 to 77.80 per cent. The maximum reduction of pod damage after three days of spraying with recorded in the plots treated with spinosad 0.01 per cent was 77.80 per cent reduction and followed by indoxacarb 0.01 per cent and fipronil 0.01 per cent with 72.52 and 71.29 per cent reduction respectively. The next effective treatments were Ha NPV 1 ml/ l, azadirachtin 5 ml/ l, NSKE 10.00 per cent, neem oil 1.00 per cent was 71.39, 70.12, 64.15 and 60.02 per cent reduction respectively, which were at par with each other. The minimum reduction of 42.79 and 35.88 per cent was recorded in plots treated with neem leaf extract 10.00 per cent and B. bassiana 1 g/ l which were inferior to all the other insecticidal treatments. The per cent reduction after seven and fifteen days of application of treatments with the similar trend and proved significantly superior over control. Singh et al., (2014) revealed that Indoxacarb 14.5 SC was effective for H. armigera management. Yadav et al., (2015) also showed that Indoxacarb 14.5 SC was most effective in reducing the pod borer damage and approximately similar results were found by Sonune et al., (2010), Daharia and Katlam (2013) and Gadhiya et al., (2014).
 
Effect of insecticides and biopesticides on the seed yield of greengram
 
The data presented in the (table 2) revealed that all the plots treated with insecticides and biopesticides gave significantly higher seed yield over control (4.33 q ha^-1). The maximum seed yield of 9.13 q ha^-1 was obtained in the plots treated with spinosad 45 SC followed by indoxacarb 14.5 SC (8.89 q ha^-1) and fipronil 5 SC (8.60 q ha^-1) which were found statistically at par with each other. The seed yield (8.13 q ha^-1) obtained in the treatment of Ha NPV which was at par with treatment of azadirachtin 0.03 EC (8.06 q ha^-1), followed by the treatment NSKE 10.00 per cent with seed yield (7.93 q ha^-1). The minimum seed yield of (5.26 q ha^-1) was obtained in the plots treated with B. bassiana 1.15 WP followed by the treatment neem leaf extract (6.10 q ha^-1) which was found statistically at par with each other. Jat et al., (2012), Chandel et al., (2014), Sharma et al., (2014) reported that the highest yield was recorded in spinosad 0.01 per cent followed by indoxacarb 0.01 per cent plot.
 

 
Economics of insecticides and biopesticides
 
The highest benefit cost ratio was obtained from the plot treated with Neem oil 1.0 per cent (11.11:1), followed by NPV 1 m/l (10.80:1), NSKE (8.26:1), indoxacarb 0.01 per cent (5.73:1), neem leaf extract (4.94:1), azadirachtin (4.37:1), fipronil 0.01 per cent (3.80:1), spinosad 0.01 per cent (3.75:1) these treatment were proved to be most economic (Table 3). The lowest benefit cost ratio was computed in the plot treated with B. basssiana (1.11:1). The findings get full support from Gautam et al., (2018) who reported maximum benefit cost ratio in neem oil 5 ml/ l and followed by NSKE.
 

Out of nine treatments evaluated against gram pod borer, H. armigera and spotted pod borer, M. testulalis. The spinosad 45 SC (0.01%) proved to be most effective, indoxacarb 14.5 SC (0.01%)  followed by fipronil 5 SC (0.01%), whereas, treatments of neem leaf extract (10.00%), Beauveria bassiana 1.15 WP 1X108 spore/ l proved to be least effective. The maximum seed yield of 9.13 q ha^–1 was obtained in the plots treated with spinosad 45 SC (0.01%) followed by indoxacarb 14.5 SC (0.01%) (8.89 q ha^-1), fipronil 5 SC (0.01%) (8.60 q ha^-1). The highest benefit cost ratio was obtained from the plot treated with neem oil 1.00 per cent (11.11), followed by Ha NPV 1m/ l (10.80), NSKE (8.26), indoxacarb 0.01 per cent (5.73), neem leaf extract (4.94), azadirachtin (4.37), fipronil 0.01 per cent (3.80) and spinosad 0.01 per cent (3.75).